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Multiple Standards Develop Frame relay is a protocol defined by both ANSI and ITU-T

Frame Relay, Part 2 - Application, Services, and Design. Multiple Standards Develop Frame relay is a protocol defined by both ANSI and ITU-T Frame relay derives from the Link Access Protocol-D (LAP-D) signaling portion of the new ISDN signaling standard

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Multiple Standards Develop Frame relay is a protocol defined by both ANSI and ITU-T

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  1. Frame Relay, Part 2 - Application, Services, and Design Multiple Standards Develop • Frame relay is a protocol defined by both ANSI and ITU-T • Frame relay derives from the Link Access Protocol-D (LAP-D) signaling portion of the new ISDN signaling standard • Frame relay is also a transport technique offered by many network providers • Frame relay is a connection-oriented frame mode bearer service • Both ANSI and ITU-T ISDN standards use the LAP-D data link layer and the ANSI standard has provisions to supplement frame relay using the LMI extensions

  2. Frame Relay, Part 2 - Application, Services, and Design • Frame relay is sometimes confused with the term “fast packet” • Fast packet is a generic term used for many high-speed packet technologies, such as frame relay and cell relay, and has been used to represent multiplexer upgrades to faster X.25 packet switching • Frame relay and frame switching are synonymous only with the ITU-T switching implementation of frame relay called type II • The LMI specifications span both standards organizations

  3. Frame Relay, Part 2 - Application, Services, and Design ITU-T/CCITT Standards • ITU-T standards are given numbers with letter prefixes • The “I” recommendations tend to provide the framework for services, protocols, and operations • The “Q” recommendations tend to define the detailed operations of subjects such as signaling, transport, and implementations • Frame relay shares much o fits architecture and protocol structures with the ITU-T ISDN standards • Frame relay is referred to as an end-user service under the ISDN bearer services standards. This defines frame relay as an “interface” between the user and the network service

  4. Frame Relay, Part 2 - Application, Services, and Design ITU-T/CCITT Standards (Continue…) • The addressing of frame relay is defined through Data Link Connection Identifiers (DLCIs), enabling multiple logical channels (PVCs) per a single physical interface • ITU-T also calls for three functions to be implemented in the upper half of the layer two: link utilization, flow control, and error recovery • These functions are often performed by the user DTE equipment or other higher-level protocol implementations such as TCP/IP

  5. Frame Relay, Part 2 - Application, Services, and Design ITU-T/CCITT Standards (Continue…) • ISDN standards are at the root of frame relay protocol operation • There are two main types of frame relay defined:\ • Type I : private or virtual private frame relay • Type II : public frame relay

  6. Frame Relay, Part 2 - Application, Services, and Design ANSI Standards • Many of the ANSI standards are designed to complement the ITU-T ISDN Recommendations • While many frame relay implementations comply with ANSI standards, it is the LMI specifications with extensions that made early implementations of frame relay possible • These interface specifications are enhanced by the LMI extensions as defined by the “Gang of Four” (StrataCom, Digital Equipment Corporation, Cisco Systems, and Northern Telecom)

  7. Frame Relay, Part 2 - Application, Services, and Design ANSI Standards (Continue…) • ANSI T1.617, T1.618, and T1.606 provide customer interface standards for access speeds of DS0, Nx56 kbps, Nx64 kbps, and DS1, primarily defining the user-to-network interface (UNI) and the network-to-network interface (NNI) • Annex D and NNI, along with LMI, are the most common implementations • Both permanent virtual circuits (PVCs) and Switched Virtual Circuits (SVCs) provide call connection service via the ANSI standards

  8. Frame Relay, Part 2 - Application, Services, and Design LMI Extension and Proprietary Solutions • These extensions have features which, even though they are of a proprietary implementation, complement and supplement both the ANSI and ITU-T standards, as well as represent the views of private and public network suppliers • This common platform of the Gang of Four for interoperability has become the de facto standard in the industry for the interconnection of CPE equipment, via a frame relay access interface, to frame relay switches • These proprietary LMI features handle the information exchange between the network and user-attached devices, providing standards for such things as support of automatic reconfiguring of devices and fault detection

  9. Frame Relay, Part 2 - Application, Services, and Design LMI Extension and Proprietary Solutions (Continue…) • LMI features also enhance service by providing the user with status and configuration information on the PVCs active at that time. • OSRM level 1 connectivity is also addressed, along with customer network-management functions • Refer to Figure 11.1 (p. 420) • There are two types of LMI extensions: • standard: is used by almost every major CPE vendor offering a frame relay interface for its equipment • optional: is not used and some options remain under development

  10. Frame Relay, Part 2 - Application, Services, and Design Standard LMI Extensions • The standard LMI extensions perform the following functions: • Notify user of PVC status (active and present DLCI) • Notify user of add/delete/change PVC • Notify user of physical link “keep-alive” signal and logical link status

  11. Frame Relay, Part 2 - Application, Services, and Design Optional LMI Extensions • Multicast capabilities: allow multiple LAN interconnected user devices to function with simpler address resolution • Flow control: enhancements to congestion indication and user notification • Global addressing convention: allows the network to provision DLCIs on a port-by-port basis • Asynchronous status updates: allows he network to notify the user device of a change in logical channel DLCI status

  12. Frame Relay, Part 2 - Application, Services, and Design FR Parameters and Sizing Calculating the Committed Information rate (CIR) and Excess Information Rate (EIR) • The CIR is a quality-of-service measurement that provides a “statistically guaranteed” rate of throughput on the transmit or receive path of a PVC during any one period of time • The CIR is computed as the number of bits in a committed Burst size,Bc, that can arrive during an averaging interval T such that CIR = Bc/T

  13. Frame Relay, Part 2 - Application, Services, and Design Calculating the Committed Information rate (CIR) and Excess Information Rate (EIR) (Continue…) • If the number of bits that arrive during the interval T exceeds Bc, but is less than an excess threshold, Bc + Be, then the subsequent frames are marked as Discard Eligible (DE) • Setting T to a value on the order of the ground trip delay is a good guideline to achieve good TCP/IP throughput over frame delay • In public FR service it is the responsibility of the provider to set the value of T, and the value of 1 is often used to match the private line measure of bps

  14. Frame Relay, Part 2 - Application, Services, and Design CIR Sizing • CIR rates in public frame relay networks are chosen for each PVC based on perceived traffic minimums and peak maximum • This measurement is made for both traffic transmitted and received by the FR access port • Two types of architecture • open-loop: frames that exceed the CIR are typically marked DE • closed-loop: the switch will not allow the CIR to be exceeded unless there is end-to-end bandwidth available across the network to transmit the frame

  15. Frame Relay, Part 2 - Application, Services, and Design CIR Sizing(Continue…) • Some providers (e.x. MCI) offer the subscriber the capability to use additional bandwidth over and above the CIR, marking all traffic above the CIR as DE ( statistical approach) • CIR rates are typically chosen based on the type of traffic and protocol being transmitted and the time required to get information from origin to destination • Refer to Figure 11.2 (p. 424) • Some public frame relay network providers offer the option of utilization reports (tell the user by PVC, for each direction, what the peak, average, and maximum average traffic load is at any time

  16. Frame Relay, Part 2 - Application, Services, and Design FR Access Port Sizing • FR access ports come in many speeds, from 56 kbps, through 56/64 kbps increments, up to and including DS1 (1.544 Mbps) and DS3 (45 Mbps) • All PVC CIR rates both into and out of the FR access port should be added separately • The combined CIR speed in either direction should not exceed the port speed in either direction, unless you plan to oversubscribe the port • Refer to Figure 11.3 (p. 426)

  17. Frame Relay, Part 2 - Application, Services, and Design Unidirectional, Asymmetrical, or Simplex PVCs • Even though a PVC offers a full-duplex connection, CIR rates are assigned unidirectionally • Each PVC is assigned two CIRs - one for each direction-transmit and receive • There is the capability in some frame relay networks to assign different CIRs to each direction of the PVC. These are called unidirectional, asymmetrical, or simplex CIRs • These CIRs dictate a small size request in one direction that triggers a large file transfer in the opposite direction as in an inquiry/response application • Refer to Figure 11.4 (p. 427)

  18. Frame Relay, Part 2 - Application, Services, and Design Bursting over CIR • In most cases, the transmitted traffic throughput will exceed the assigned CIR. This is referred to as “bursting” • Refer to Figure 11.5 (p. 428) • Bursting over CIR may not have a good effect on applications during congestion conditions, but most of the time multiple PVCs sharing the same UNI access circuit will not transmit data at the exact same moment • This leads to good statistical multiplexing on access ports, and in these instances FR can provide significant response time savings

  19. Frame Relay, Part 2 - Application, Services, and Design Discard Eligible (DE) • There are many ways to limit the amount of bandwidth provided to a user at any time • One method of delimiting the bandwidth to select users on a priority basis is through the intellifent and selective use of the Discard Eligibility (DE) bit • User frames with DE set to 1 are discarded first. Higher-priority users would have DE set to 0 • The Discard Eligible (DE) bit may be set by either the customer or by the network • Other methods employ proprietary implementations

  20. Frame Relay, Part 2 - Application, Services, and Design Oversubscription • There are two different ways in the setting of the CIR • regular booking: the sum of the CIRs is no more than the access rate • overbooking or oversubscription: the sum of CIRs exceeds the access line rate (statistical approach) • Oversubscription is the capability to oversubscribe or overbook the CIRs coming into a single physical access port • High oversubscription rates can yield greater throughput and savings in equipment and local loop costs • Oversubscription is typically chosen when users intimately understand their PVC traffic patterns and utilization

  21. Frame Relay, Part 2 - Application, Services, and Design PVC Reroute Capability • IF a physical path on which a PVC rides is broken, the FR switches at both ends of the physical path can route the PVC via an alternate switch to the end switch destination • This capability does not exist for the UNI, only within the FR-switched fabric

  22. Frame Relay, Part 2 - Application, Services, and Design Congestion in Frame Relay Networks Defined • Network congestion occurs when the traffic attempting to be passed across a specific portion of the network fabric is greater than the available bandwidth • When the network reaches a congestion point it will begin to discard frames using DE bit priorities • The user or network access devices must have the intelligence of higher-level protocols to provide end-to-end error detection and correction and retransmission of missing data

  23. Frame Relay, Part 2 - Application, Services, and Design Congestion in Frame Relay Networks Defined (Continue…) • There are two types of congestion-control methods • Implicit: congestion notification implies the use of a layer 4 transport protocol, such as TCP or SNA, in either the network device or the user premises equipment • Explicit: congestion notification comes in three flavors • FECN: bit is set by the FR network nodes when they become congested and this informs the receiver flow-control protocols of the congestion situation • BECN: bit is set in FR frames headed in the downstream direction to inform a transmitter flow-control protocols of the congestion situation

  24. Frame Relay, Part 2 - Application, Services, and Design • CLLM: can contain a list of DLCIs that correspond to the congested frame relay bearer connections- all users affected are then notified of congestion. Multiple CLLM messages can be transmitted in a network with many DLCIs that require congestion notification Public Network FR Services Service Aspects of Frame Relay • Frame relay is offered as a frame-based public data service that allows access line speeds up to 1.544 Mbps from a Customer Premises Equipment (CPE) router, bridge, or Frame Relay Access Device (FRAD) into the public frame relay network

  25. Frame Relay, Part 2 - Application, Services, and Design Service Aspects of Frame Relay (Continue…) • FR network trunks can be of speeds from DS0 (56 kbps) up to and including DS3 (45 Mbps). Dial-up access to frame relay is also available • Public frame relay services offer different interpretations of the Committed Information Rate (CIR) and Discard Eligible (DE functions depending on the network switching architecture used). • Customer network management, performance reporting, configuration and information management, and various fixed and usage-based billing services are offered by service providers.

  26. Frame Relay, Part 2 - Application, Services, and Design Public versus Private • Public frame relay service provides a consolidation of private line meshing, instead performing the meshing through PVCs within the FR network and requiring each user to have a single access circuit to the public network • Refer to Figure 11.9 (p. 438) • Private frame relay network designs are based on three types of technologies • DS1/DS3 multiplexers employing fast-packet frame relay technology and interface cards • Bridges or routers employing dedicated links for frame relay interfaces into a network • Fast-packet switches employing dedicated DS1/DS3

  27. Frame Relay, Part 2 - Application, Services, and Design Public Frame Relay Service Offerings • There are three main groups providing public frame relay services: what were traditionally the ICCs, the RBOCs, and LECs, and Internet access providers • The major frame relay service providers in the United States include Ameritech, AT&T, Bell Atlantic, BellSouth, Cable & Wireless, CompuServe, GTE, MCI Communications, MFS, NYNEX, Pacific Bell, and Sprint • Most of today’s IXC frame relay public service offerings include StrataCom Integrated Packet Exchange IPX-32 with BPX, the Bay Network’s BCN and BNX frame relay switches, the Alcatel TPX1100, the Cascade STX-9000s, or the AT&T BNS-2000

  28. Frame Relay, Part 2 - Application, Services, and Design Switched Virtual Circuits (SVCs) • Both ANSI and ITU-T have published standards for Switched Virtual Circuit (SVC) frame relay operation • SVC service offers an excellent opportunity to users requiring • Short connect, low volume, and transfer times with infrequent connectivity and traffic patterns • Connectivity provisioned on-the-fly • Backup for PVC failure over dial access (POTS line or ISDN) to FR switch

  29. Frame Relay, Part 2 - Application, Services, and Design Switched Virtual Circuits (SVCs) (Continue…) • SVCs allow a sending DTE to transmit the address of the receiving DTE along with the data at call setup time • When the first switch receives this address and data, it establishes the connection-oriented, virtual path to the receiver • This method eliminates the need for preconfigured PVCs

  30. Frame Relay, Part 2 - Application, Services, and Design Network-to-Network Interface (NNI) • The FR Network-to-Network (NNI) is defined by the standards as a method for two frame relay networks to interconnect, pass frame relay traffic, and manage the logical connections (PVCs) which originate on one frame relay network and terminate on another • Refer to Figure 11.10 (p. 441) • NNI circuits are also used to connect dissimilar switch types, as is usually the case between different FR services, providing multivendor interoperability

  31. Frame Relay, Part 2 - Application, Services, and Design Frame Relay Service Provider Interconnectivity Issues • Frame relay interconnectivity between service providers is just now beginning to proliferate • There is a published Frame Relay Forum (FRF) Implementers Agreement for the Network-to-Network (NNI) interface that almost everyone follows

  32. Frame Relay, Part 2 - Application, Services, and Design Public Frame Relay Network Architectures Open-Loop Architecture • Open-loop algorithm systems operate on the concept of congestion control after congestion begins to occur • In an open-loop architecture, each user (PVC) is allocated a committed burst size or CIR • Users can transmit all their traffic and not mark any frames discard eligible (DE) if the committed burst (CIR) is not exceeded • It is up to the applications to use some method to back-off-and-retransmit while the network recovers from congestion

  33. Frame Relay, Part 2 - Application, Services, and Design Open-Loop Architecture (Continue…) • Refer to Figure 11.12 (p. 446) • Pure noncell frame switches typically use open-loop congestion algorithms • Frame relay switches that do not use cell switching will typically read the entire frame into buffers before transmitting it to the user or next switch • Applications that react by retransmitting lost frames will cause congestion to intensify even further • Window-sizing flow-control protocols such as TCP can be used to scale down the volume of retransmissions and spread the load over a greater time period

  34. Frame Relay, Part 2 - Application, Services, and Design Closed-Loop Architecture • A closed-loop architecture is typically found in switches that convert frames to fixed-size cells on the backbone • These switches immediately slice frames into cells and transmit the data, thus incurring less serialization delay • The closed-loop architecture creates a closed environment, where every switch within the FR network fabric knows the congestion condition from origin to destination • The FR network prevents the user from experiencing lost data due to congestion by slowly throttling back the available transport bandwidth at the user entry point to the FR network (UNI) to the predefined CIE rate • Refer to Figure 11.13 (p. 448)

  35. Frame Relay, Part 2 - Application, Services, and Design FR over a Cell-Relay Backbone • When frames are segmented into cells and transmitted as soon as there is enough data to fill up a cell, the end-to-end delay can be decreased. • The frame relay switches do not have to wait until entire frame is read into buffers before segmenting into cells and transmitting • Serialization delay is decreased and end-to-end jitter is also reduced

  36. Frame Relay, Part 2 - Application, Services, and Design Access Design Issues Network Access Devices • A variety of hardware devices exist on the market that make frame relay network access possible (bridges, routers, gateways, FRADs, multiplexers, voice switches, etc.) • Much of the protocol conversion, processing, and switching is done through software. This minizes the hardware investment required to upgrade FR • When purchasing frame relay access or switching hardware, ensure that the equipment is compatible with the standards mentioned

  37. Frame Relay, Part 2 - Application, Services, and Design Network Access Devices (Continue…) • Primary difference between fast-packet and frame relay switching is that fast-packet multiplexers still have dedicated paths for the data, while frame relay routers are based upon the DLCI in the address field • A true frame relay device has the flexibility of “dynamically allocating” all available bandwidth to whatever application needs it at a given time

  38. Frame Relay, Part 2 - Application, Services, and Design Frame Relay Access Device (FRAD) • The FRAD performs the framing function, placing the user protocol into a FR frame • Refer to Figure 11.14 (p. 451) • The FRAD provides the connectivity to a private or public switched FR network • Access speeds are via DS0, fractional T1 (FT1), or full T1. • A FRAD can also provide an interface for LAN protocols such as Token Ring or Ethernet • FRADs contain the powerful capability to carry SNA and LAN traffic over a single interface or network access circuit, and some even provide “spoofing” or some level of PU4/PU5 emulation

  39. Frame Relay, Part 2 - Application, Services, and Design Frame Relay Access Device (FRAD) (Continue…) • FRADs can perform a level of congestion control outside the frame relay network through SDLC congestion-control techniques • Most FRADs support frame relay protocol with transparent of X.25 and SDLC protocols over frame relay PVCs and SVCs • Some FRADs also support the ISDN PRI and SMDS SNI interfaces • Refer to Figure 11.15 (p. 452)

  40. Frame Relay, Part 2 - Application, Services, and Design • A device that can be used to assist transmission of video over frame relay is the video coder/decoder (codec). • A codec can transmit pixel updates for only that portion of the video that changes • Some vendors offer the capability of placing low-quality voice over FR, such as Motorola, Hypercom, and Micom. This feature is especially attractive with international communications

  41. Frame Relay, Part 2 - Application, Services, and Design Dial Access and Dial Backup • Users that are typically located at remote sites that do not need continuous connectivity and cannot justify the expense of a dedicated line, can use dial up access • Dial access provides the capability to dial into a dedicated network device, such as the FR switch and terminal server • Refer to Figure 11.16 (p. 454) • Dial access can also provide dial backup should a primary, dedicated link fail or something else goes wrong. • Refer to Figure 11.17 (p. 454) • Dial backup can be initiated outside the FR • Refer to Figure 11.17 (p. 455)

  42. Cisco Configuring Novell IPX

  43. Objectives • Identify the network and host in an IPX address • Configure IPX on a Cisco router and configure interfaces • Configure multiple encapsulations on an interface by using secondary interfaces and subinterfaces • Monitor and verify IPX operation on the router

  44. Introduction to Novell IPX • Novell IPX Protocol Stack and the OSI Model • IPX • SPX • RIP • SAP • NLSP • NCP

  45. IPX Protocol Stack and the OSI Model

  46. Client-Server Communication • NetWare servers provide the following services to clients: • File • Print • Message • Application • Database

  47. Remote IPX Clients on a Serverless Network

  48. Server-Server Communication • Service Advertising Protocol (SAP) • Routing Information Protocol (RIP)

  49. Encapsulation Ethernet Token Ring FDDI IPX Addressing

  50. Multiple Frame Types on a Single Ethernet Segment

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